Differential flash memory programming technique

ABSTRACT

The invention relates flash memory programming techniques. An object of the invention is to provide a flash memory programming technique avoiding problems of the known state of the art and in particular, saving a significant amount of time during the development and/or production phases of any equipment containing flash memory devices and also saving time during an updating or upgrading procedure of such an equipment already being in use. Accordingly, the invention proposes for programming a flash memory device to program only differences in information between data already stored in the flash memory device and new data to be stored.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 11/943,502, entitled “DIFFERENTIAL FLASH MEMORY PROGRAMMING TECHNIQUE,” filed on Nov. 20, 2007, by Martin A. Lose, et al., which is currently pending and is a continuation of U.S. Pat. No. 7,313,030, entitled “DIFFERENTIAL FLASH MEMORY PROGRAMMING TECHNIQUE,” filed on Jan. 22, 2003, and issued on Dec. 25, 2007, by Martin A. Lohse, et al., and is a continuation of EPO application 02002166.3, filed on Jan. 29, 2002. The above-listed applications are commonly assigned with the present invention and are incorporated herein by reference as if reproduced herein in their entirety.

TECHNICAL FIELD OF THE INVENTION

The invention relates to a method for differentially flash memory programming, to a flash memory programming apparatus having such functionality and to a flash memory device processed by applying that functionality.

BACKGROUND OF THE INVENTION

Generally, flash memory devices are used widely because of their low costs and ability to retain data when power is shut off. Moreover, they are rewritable many times and use a block erase technique as opposed to EEPROM's. Consequently, flash memories devices are often used inside apparatuses for storing applications and/or other data, such as inside handhelds and cell phones.

However, the in-circuit programming of such flash memory devices by known conventional techniques requires at least approximately 2.5 minutes of programming time for each megabyte of data.

In particular, during the development of new applications or corresponding programs, during the production phases and/or even in case of the updating or upgrading of an existing application and/or implemented software, it is often the case that the respective program changes to be made are small relative to the entire flash size. Conventional flash programming techniques however, generally reprogram the entire flash device at one time or successively, for example sector after sector or block after block to which the flash memory device usually is divided. As a result, the rewriting or reprogramming of the flash memory device is slow no matter how small the actual change may be.

For example, current mobile phones contain flash memory devices up to four megabytes in size, which represents a total programming time during any development, production and/or upgrading phases of approximately ten minutes.

SUMMARY OF THE INVENTION

An object of the invention is therefore to provide a flash memory programming technique avoiding the discussed problems of the known state of the art and in particular, saving a significant amount of time during the development and/or production phases of any equipment containing flash memory devices and also saving time during an updating or upgrading procedure of such an equipment already being in use.

Accordingly, the invention proposes for programming a flash memory device to program only differences in information between data already stored in the flash memory device and new data to be stored.

Consequently, since in case of an information change or update only the differential information is newly programmed the total programming time is directly related to the amount of differences between the new data and the data already present in the flash memory device. As a result thereof, in particular, if the information changes in fact result in small differences with regard to the total flash size, a significant reduction of total programming time is ensured.

Preferably, it is further proposed that volatile information or volatile software components are stored at least near the end of the respective flash memory address space of the flash memory device to keep the need of changing or adjusting flash sectors, in particular with regard to necessary sizes and/or the amount, as slight as possible.

To further reduce such need of changing or varying flash sectors, according to a further preferred embodiment, it is proposed to store the differential information at least near the end of the respective flash memory address space of the flash memory device.

In addition or as an alternative, it is further proposed to store information least likely to be changed at least near the beginning of the respective flash memory address space of the flash memory device.

According to a further refinement, the placing of stored information and/or information to be stored, in particular even a determinable placing thereof, is supervised preferably by means of an appropriate adapted software linker means, in particular to improve the flexibility during succeeding phases of a development process.

Preferably, for ensuring an accurate data comparison between the new data to be programmed with that already present in the flash memory device to detect the differences in information, a cyclic redundancy check is employed, in particular by using correspondingly adapted logical comparing means.

Correspondingly, the invention is further providing a flash memory programming apparatus adapted to employ the inventive functionality and preferably comprising means for selectively erasing and/or reprogramming a sector having a difference in the embedded data with regard to the respective new or updated data to be stored. Moreover, the invention is covering a flash memory device processed by such functionality and a software implementation product adapted to perform that inventive method.

BRIEF DESCRIPTION OF THE DRAWING

Subsequently, the invention is described in more detail with regard to a preferred embodiment and based on the accompanied drawing, in which:

FIG. 1 a is schematically depicting an exemplar arrangement of sectors of a flash memory chip depending on the likelihood of changing of the respective data embedded therein prior to performing an information change, and

FIG. 1 b is schematically depicting the exemplar arrangement of FIG. 1 a after an information change.

DETAILED DESCRIPTION

A plurality of further software projects or applications and hence, a plurality of flash memory devices such as flash memory chips, contain a significant amount of libraries and constant data that almost never will be changed. On the other hand side however, certain software sections, especially during a development and/or production phase and/or due to an updating or upgrading process, will change greatly and hence forming volatile information or software components stored in flash memory devices.

Regarding FIGS. 1 a and 1 b, an exemplar flash memory chip divided in several addressable sectors or blocks 101 . . . 107 with information or software components respectively embedded therein is schematically depicted. A current mobile phone for example, contain such flash memory chips with an entire size of up to four megabytes. Thus, in case of an information change, for example during the development and/or production phase because of the detection of errors or problems in some of the software components, a total programming process for changing the entire data or information stored would result in an programming time for each mobile phone of approximately ten minutes.

According to the inventive approach however, in particular by programming only the differences in information between the new data and the data already stored in the flash device, software changes which generally result in small differences in flash data, require only a few seconds to program.

Based thereon, volatile software components are physically arranged preferably at least near the end of the respective flash memory address space of a flash memory device and the least likely to change components are preferably placed near the beginning.

Referring to FIGS. 1 a and 1 b in more detail, FIG. 1 a is schematically depicting the exemplar flash memory chip prior to performing a software change. Based on FIG. 1, information components least likely to be changed are placed or stored at the beginning of the respective flash memory address space, for example in the depicted sectors 101 to 104. Within the sectors 105 and 106 and possibly following sectors, information components are embedded which will be changed greatly.

As mentioned above, during a development and/or production phase such volatile information or software components are fraught with problems, for example. If the flash memory chip is already in use, for example inside a mobile phone, such volatile information components may comprise stored addresses or other applications which depend on actual standards.

If a problem or error is detected and identified or an application has to be upgraded due to a new standardisation, the information components already stored in the flash memory device, i.e. within the sectors 101 to 106 is compared with the respective new information or updated set of data. This is performed preferably by using a correspondingly adapted logical comparator of an associated programming apparatus, as known in general by person skilled in the art. To ensure that the data comparison is always accurate such logical comparator preferably employs a cyclic redundancy check (CRC).

If the logical comparator is identifying an information difference in sectors 105 and 106 of the flash memory chip of FIG. 1, then only these two sectors 105 and 106 are erased and newly written as indicated by the depicted arrows, without the need of changing the preceding sectors 101 to 104. Moreover, since the flash memory chip prior to the information change (FIG. 1 a) has still memory address space left, a new succeeding sector 107 can be defined and written to add a differential or completely new information component without the need of changing the preceding sectors 101 to 104.

The arrangement after such an information change and/or adding is schematically depicted in FIG. 1 b.

As can be seen from FIG. 1 b, the sizes of the information components within the sectors 105 and 106 after the information change are different in comparison to the situation prior to the information change, as depicted in FIG. 1 a. In particular, the exemplar information change has reduced the amount of the set of data embedded in sector 105 but has enlarged the amount of the set of data embedded in the sector 106.

Accordingly, if the volatile information component embedded in sector 105 would have been embedded for example, in sector 103 prior to the information change, then after the information change flash memory address space would be unused and wasted except when the entire flash memory device is reprogrammed to correspondingly adjust the sector sizes. Similar thereto, if the volatile information component embedded in sector 106 would have been embedded for example, in sector 104 prior to the information change, then all of the succeeding sectors should be changed or newly adjusted, i.e. erased and newly written, since the information change causes an enlargement of that volatile information component stored in sector 106. As it is obvious for a person skilled in the art, a same or corresponding consequence due to the information change should be applied to the information component newly added in sector 107 having a very high address in case of adding such information component within a sector having a lower address.

It is mentioned, that the placement or ordering of the respective software components may be controlled by the respective associated software linker, which may supervise a pre-determinable placing of a stored information component or information component to be stored, in particular depending on its likelihood of changing. Consequently, the information components according to FIG. 1 b may be additionally or subsequently re-ordered, in particular depending on a variation in the likelihood of changing the respective information components.

As it is obvious for person skilled in the art, the inventive approach is not restricted to the example of a mobile phone containing flash devices. In general any product and/or application that requires in-circuit reprogramming of flash memory devices may use the inventive approach for programming flash memories such that the programming time is directly related to the amount of differences between the data already present in the flash and the new data to be stored. 

1. A method for flash memory programming comprising the steps of: programming only differences in information between data presently stored in a flash memory device and new data to be stored therein; and supervising the placing of stored information or information to be stored.
 2. A method of claim 1, further comprising the step of storing volatile information at an address near the end of the respective flash memory address space of the flash memory device.
 3. A method of claim 1, further comprising the step of storing differential information at least near the end of the respective flash memory address space of the flash memory device.
 4. A method of claim 1, further comprising the step of storing substantially constant information at least near the beginning of the respective flash memory address space of the flash memory device.
 5. A method of claim 1, further comprising the step of performing a cyclic redundancy check between data already stored in the flash memory device and data to be stored to ensure an accurate data comparison.
 6. A method of claim 1, further comprising the step of storing differential information at least near the end of the respective flash memory address space of the flash memory device.
 7. A flash memory device comprising several erasable and programmable sectors with defined data embedded therein, characterized in that placing of the embedded data and data to be stored is supervised including ordering the embedded data within the sectors based on if the embedded data is substantially constant.
 8. A method for flash memory programming comprising the steps of: programming only differences in information between data presently stored in a flash memory device and new data to be stored therein; and storing volatile information at an address near the end of the respective flash memory address space of the flash memory device.
 9. A method for flash memory programming comprising the steps of: programming only differences in information between data presently stored in a flash memory device and new data to be stored therein; and storing substantially constant information at least near the beginning of the respective flash memory address space of the flash memory device.
 10. A method for flash memory programming comprising the steps of: programming only differences in information between data presently stored in a flash memory device and new data to be stored therein; and performing a cyclic redundancy check between data already stored in the flash memory device and data to be stored to ensure an accurate data comparison. 